Iodoethane → 6'-bromo-4-ethoxyspiro[cyclohexane-1,2'-inden]-1'(3'H)-one

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Reaktionsschritte

6′-Bromo-4-hydroxyspiro[cyclohexane-1,2′-inden]-1′(3′H)-one as a 2:1 mixture of isomers (Intermediate 5 Step 2, 10.4 g, 34.1 mmol) and ethyl iodide (3.6 mL, 44.3 mmol) were dissolved in 2-MeTHF (100 mL) under N2. KOt-Bu (7.65 g, 68.2 mmol) was added portionwise to the reaction mixture, keeping the internal temperature below 30° C. The solution was stirred at r.t. overnight. Water (40 mL) and brine (25 mL) were added and the mixture was further stirred for 5 min. The mixture was diluted with brine and 2-Me-THF until two layers formed. The phases were separated. Activated charcoal was added to the organic layer which was then stirred for 10 min. Diatomaceous earth was added and the mixture was further stirred for 5 min. The mixture was filtered through a plug of silica gel and diatomaceous earth, which was rinsed with heptane/EtOAc 7:3. The filtrate was concentrated. The filtration sequence was repeated, affording 4.0 g (36% yield) of the title compound (as a 2:1 mixture of isomers): 1H NMR (300 MHz, CDCl3) ppm 1.22 (t, 3 H), 1.32-1.45 (m, 2 H), 1.45-1.52 (m, 2 H), 1.77 (dt, 2 H), 2.07-2.16 (m, 2 H), 2.98 (s, 2 H), 3.30-3.40 (m, 1 H), 3.57 (q, 2 H), 7.34 (d, 1 H), 7.69 (dd, 1 H), 7.87 (d, 1 H).

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